To produce hydrocarbons (e.g., crude oil, natural gas, etc.) from the earth, a wellbore can be drilled that penetrates one or more hydrocarbon-bearing strata or subterranean formations, also known as reservoir formations. As used herein, the “perforated interval” or “production interval” is the section of a wellbore that has been prepared for production by creating channels between the reservoir formation and the wellbore. In many cases, long reservoir sections will be perforated in several intervals, with short sections of unperforated casing between each interval to enable isolation devices, like packers, to be set for subsequent treatments or remedial operations.
Generally, after a wellbore has been drilled to a desired depth, completion operations can be performed, which is the assembly of downhole tubulars and equipment required to enable production from an oil or gas well. Completion operations can involve the insertion of casing into a wellbore, and thereafter the casing, if desired, can be cemented into place. To produce hydrocarbon from the subterranean formation, one or more perforations can be created that penetrate through the casing, through the cement, and into the production interval.
At some point in the completion operation, a stimulation operation can be performed to enhance hydrocarbon production from the wellbore. Stimulation is a treatment performed to restore or enhance the productivity of a well. Stimulation treatments fall into two main groups, hydraulic fracturing treatments and matrix treatments. Fracturing treatments are performed above the fracture pressure of the reservoir formation and create a highly conductive flow path between the reservoir and the wellbore. Matrix treatments are performed below the reservoir fracture pressure and generally are designed to restore the natural permeability of the reservoir following damage to the near-wellbore area. Thus, stimulation operations can include hydraulic fracturing, acidizing, fracture acidizing, or other suitable stimulation operations.
After the stimulation operation, the wellbore can be placed into production. Generally, the produced hydrocarbons flow from the reservoir, through the perforations of the production intervals with the wellbore and through the wellbore to the surface.
Problems can result in stimulation operations where the wellbore penetrates multiple production intervals due to the variation of fracture gradients between these intervals. The most depleted of the production intervals typically have the lowest fracture gradients among the multiple production intervals. When a stimulation operation is simultaneously conducted on all of the production intervals, the treatment fluid can preferentially enter the most depleted intervals. Therefore, the stimulation operation often does not obtain the full benefit of the stimulation in those production intervals having relatively higher fracture gradients.
One method conventionally used to overcome problems encountered during the stimulation of a subterranean formation having multiple production intervals has been to use packers and/or bridge plugs to isolate the particular production interval before the stimulation operations. This can be problematic, however, due to the existence of open perforations in the wellbore and the potential sticking of these mechanical isolation devices.
Another method conventionally used to overcome problems encountered during the stimulation of a subterranean formation having multiple production intervals has been to perform a remedial cementing operation prior to the stimulation operation to plug the open perforations in the wellbore. This hopefully prevents the undesired entry of the stimulation fluid into the most depleted intervals of the wellbore. After the pre-existing perforations of a depleted production interval have been plugged with cement, the particular production interval can later be re-perforated, isolated, and then stimulated. While these remedial cementing operations can plug the pre-existing perforations and thus reduce the entry of the stimulation fluid into undesired portions of the formation, remedial cementing operations are often complicated and time consuming. This can require multiple remedial cementing operations to ensure complete plugging of all the pre-existing perforations. In addition, remedial cementing operations can damage near wellbore areas of the subterranean formation and/or require further remedial operations to remove undesired cement damage from the near-wellbore area before the well can be placed back into production.
What is needed in the art are improved methods to pack perforations with a consolidating proppant that will allow diversion of treatment fluids to newly perforated intervals during stimulation treatments in wellbores with a plurality of perforated intervals.